The residents of the Beaverbrook Art Gallery live by a very specific set of rules:

• Under no circumstances are residents to interact with humans or move about when there are humans in the building.
• Do not get caught outside your painting.
• Do not go into someone else's painting without his or her permission.
• Failure to abide by these rules will result in punishment and possible banishment.

Thirteen-year-old Mona Dunn is about to break the first two. But she's been trapped in the same place for more than a hundred years. So, really, who can blame her?

Twelve-year-old Sargent Singer believes in his own set of rules:

• Dad abandoned you, so don't trust him.
• This summer is going to be a disaster.
• Just get through it.
• You don't need friends.

Meanwhile, magic and mischief is brewing at the Beaverbrook. And when Sargent catches a glimpse of something unexpected and forbidden, his rules go out the window, too, and that mischief snowballs into a friendship story, a mystery, and a crime caper like no other. Exactly who is framing whom?